Diving with Fire Corals

Lanta Marine Life | Milleporidae

Fire Coral species are sessile (stationary, fixed in one place) Medusozoa, which are capable of producing calcium carbonate skeletons and forming colonies, similar to the hard corals, however these are not true corals. We can see huge colonies of fire corals when diving from Koh Lanta around Koh Rok.

Some species are important reef builders, with several species of Millepora able to very rapidly grow calcium carbonate skeletons. These skeletons are covered with countless pores which contain the polyps. Each feeding polyp is surrounded by many defensive stinging polyps which contain batteries of nematocyst cells. When touched, the nematocysts penetrate human skin and inject a powerful poison, creating the 'fire-like' burning.

In addition to capturing prey with their stinging nematocyst polyps, fire corals gain nutrients via their special symbiotic relationship with algae known as zooxanthellae, similar to the hard corals.

2 species found on this page:

Branching Fire Coral (Millepora tenella)
Leaf Fire Coral (Millepora platyphylla)

Branching Fire Coral

(Millepora tenella)

Millepora tenella @ Koh Rok

Branching Fire Coral is commonly seen at all of the dive sites around Koh Lanta. A Branching Fire Coral colony begins by encrusting a surface to form a base, and then growing outward in multiple branches.

This is a fast growing species and is capable of taking over large areas of a reef.

The colonies consist of thick, golden brown branches, with the growth zones at the tips of the branches being white.

Branching Fire Coral @ Koh Rok

Branching Fire Coral feed on plankton, and similar to true corals, due to their symbiotic relationship with zooxanthellae, they are subject to bleaching if the colourful zooxanthellae algae leave the polyps due to high sea water temperatures for example.

Fire corals can deliver a very painful burn-like sting - do not touch fire coral, you will regret it.

Leaf Fire Coral

(Millepora platyphylla)

Millepora platyphylla @ Koh Rok

Leaf Fire Coral grows vertically in leaf or plate-like branches. This species likes to grow on the top of the reef, in turbulent water (in the wave action zone) and enjoys strong sunlight which is necessary for the symbiotic zooxanthellae algae’s photosynthesis.

Leaf Fire Coral @ Koh Rok

Leaf Fire Coral is densely branched and provides shelter and home for a wide range of other species, including shrimp, frogfish, moray eels, and other small fish seeking refuge from potential predators.

As with other Fire Corals, Leaf Fire Coral can deliver a very nasty poisonous burn if touched.

Fire corals grow quickly and can push out other hard coral species to dominate some areas of a reef. Whilst this can be destructive, it can also contribute toward the survival of hard corals during Crown of Thorns outbreaks, as Crown of Thorns sea stars tend to avoid Fire Corals.